Multiple pole (also referred to as “multi-pole”) arc-fault circuit breakers (also called arc-fault circuit interrupters) are typically used in some residential applications. Contractors may elect to run two branch circuits in a three-conductor cable (two lines and one neutral) from a tie point, and connect them to a two-pole circuit breaker, reducing the cost of material and labor of installing two separate cables to the circuit-breaker panel from the individual branch circuits. This technique is known in the trade as a shared neutral, because the two circuits share the same neutral conductor back to the panel from the point where they are spliced into the three-conductor cable.
The advent of National Electrical Code (NEC) requirements for arc-fault protection on certain branch circuits has given rise to the need for two-pole arc-fault circuit breakers. In other instances, arc-fault protection may be desired for 240V loads, which also require two-pole arc-fault interrupting circuit breakers. Such circuit breakers include multiple current sensors for monitoring multiple lines. Arc faults are detected by a sophisticated algorithm run by a microcontroller in the circuit breaker. It is critical that the integrity of the sensed current from the sensors be preserved from the output of the sensor to the input of the controller to maximize detection of valid fault conditions. Any degradation or corruption of that signal could lead to faulty detection or, worse, missed detections, which would be hazardous.
What is needed, therefore, is a multi-pole circuit breaker capable of detecting arc faults occurring on any of the poles being monitored that overcomes these and other problems.